Center tubes for filters



y 1958 E. DUDINEC 2,843,269

. CENTER TUBES FOR FILTERS Filed May 16, 1955 2 Sheets-Sheet 1 INVENTOR. Emmy Duumsc BY MWM ATTORNEY July 15, 1958 E. DUDINEC CENTER TUBES FOR FILTERS 2 Sheets-Sheet 2 Filed May 16,, ess

INVENTOR. Ewan! Duouvzc Mm may! ATTORNEY United States Patent CENTER TUBES FOR FILTERS Emery Dudinec, Rahway, N. J., assignor to Purolator Products, Inc., Railway, N. J., a corporation of Delaware Application May 16, 1955, Serial No. 508,491

Claims. (Cl. 210-437) This invention relates to center tubes for filter elements and method of making same.

Replacement filter elements of the type contemplated by this invention are designed for the removal of contaminants from the liquid being filtered. Such an element is installed in a filter housing, and when clogged by contaminants is removed from the housing and discarded, and a new one installed in its place. These elements are principally composed of a resin impregnated paper that has been pleated and formed into a tubular annular pack in which the pleats extend radially of the axis of the body. An outer cover is placed over the body, a center tube inserted in the center of the annulus, and discs placed on the ends of the body and permanently sealed. Elements made in accordance with this method are more fully described in the patent to Bell, No. 2,642,187, issued June 16, 1953. As shown in Figure 3 of the above patent, the cylindrical center tube of these elements is conventionally fabricated of a material, such as metal, that is sufliciently rigid to give proper support to the inner edges of the pleats when fluid pressure tends to force them inward. The tube must also have perforations Or holes throughout its length in order to permit the liquid to flow through the tube and pass into the filter outlet. The conventional method of manufacturing these tubes involves a number of separate steps as follows:

(1) Perforating a strip of steel. (2) Cutting the strip to size.

(3) Rolling into a tube.

(4) Lock-seaming or spotwelding.

All of these steps require so much labor that the resultant cost of the part is out of proportion to the rest of the element. In addition to labor cost, there is also a certain amount of material waste, as the pieces of metal which are punched out are wasted.

The object of this invention, therefore, is the construction of anew center tube which can be made in one step, instead of four, to save a large percentage of the labor costs, and eliminate the loss of material. At the same time, the resultant tube will be strong and rugged and will combine the rigidity required to support the pleats, with a sufficiently large open area to permit proper drainage. This object is carried out by the use of a pair of mating dies which will be brought together on a strip or sheet of material, resulting in a tube in which the surface area is 50% open.

Other objects and features of the invention will be apparent from the following description and drawings in which:

Figure l is a side view of the dies and the sheet before forming.

Figure 2 is an end view of the dies and sheet of Figure 1.

Figure 3 is an isometric view of the dies and tube just at the moment of formation.

Figure 4 is an isometric view of the completed center .tube.

2,843,269 Patented July 15, 1958 Figure 5 is a vertical sectional view of a conventional filter element assembled with the center tube of Figure 4.

Figure 6 is a side view of a modified form of the dies.

Figure 7 is a side view of a modified form of the center tube fabricated by the dies of Figure 6.

Figure 8 is a side view of another modified form of the dies.

Figure 9 is a side view of another modified form of the center tube fabricated by the dies of Figure 8.

Turning to the drawings and particularly to Figures ,1 to 4, the principal form of the center tube is fabricated by means of a pair of dies which are fixed in a standard power press (not shown) in a conventional manner. The upper die 11 and lower die 12 are identical in structure but are merely inverted with respect to each other. The upper die 11 consists of a main block 13 which is rectangular in cross-section and surmounted by a number of identical plates or raised portions 14 that are approximately semi-circular in section except for :a shoulder 15 at one end of each plate. The plates are separated from each other by gaps or recessed portions 16, each gap approximately equal to the thickness of each plate. The die may be fabricated by mounting each plate 14 on the main block 13 so that the proper spacing is maintained, or by machining it out of a single piece of metal. The lower die 12 is similar to the upper die 11 and consists of main block 17, plates 18 with shoulder 19, each plate separated by gap 20.

When the forming is to begin, a sheet 21 is passed between the dies. The composition of sheet 21 may vary according to the type of center tube desired, which depends on the use to which the completed :filter element is to be put. For example, it may be made of various types of steel, ranging from mild to stainless, aluminum, magnesium, or other metals. It may be made of such plastic materials as the polyvinyl chlorides, tetraflu-orethylenes, polystyrenes, polyethylenes, or the acrylics. It may also be made of cellulosic materials, such as paper, either resin-impregnated or plain. The sheet 21 is dimensioned to make the center tube of the desired size, and can be varied to conform with the size of the dies so that tubes of any desired length or diameter can be made.

The center tube 22 is formed in the following manner. When the dies 11 and 12 are brought together by the press, each plate 14 of the upper die 11 will punch and form the portion of sheet 21 that it strikes, and force it downward into one of the gaps 20 of the lower die 12 which is aligned with the plate. At the same time, each plate 18 of the lower die 12 will similarly punch a portion of the sheet and form it upward into a gap 16 of the upper die 11. As the two dies continue toward each other, all of the upper plates 14 will pass through gaps 20 and simultaneously reach the end of their travel limited by semi-circular channels 23 on the upper portion of the block 17 of the lower die, as shown in Figure 3. Approximately one half of the sheet 21 will be fully formed between the outer periphery of the plate 14 and channels 23 into radial semi-circular strips 25, forming the lower demi-cylindrical portion 26 of the completed cylindrical center tube 22 shown in Figure 4. At the same time, all of the lower plates 18 will pass through gaps 16 of the upper die and will simultaneously reach the limit imposed by semi-circular channels 24 on the lower portion of the block 13 of the upper die. The other half of the sheet 21 will be formed between the outer periphery of the plates 18 and channels 24 into radial semi-circular strips 27 which form the upper demicylindrical portion 28 of the tube 22. Each of these halves will therefore combine to form a complete cylindrical tube. The dimensions of the die and the plate have been so designed that even at the end of the travel a portion of the sheet 21 is not formed between the plates and the channels in order that material may remain to tie the two halves 26 and 28 together. This remaining material is in the form of longitudinal seams 29 and 30 as bestshown in Figure 4. While these seams must serve to tie the halves together, they-should not .be allowed to extendout from the circumference of the completed tube, or they would interfere with the assembly of the completed element. The shoulder of the upper die 11, and the shoulder 19 of the lower die 12, prevent the undesired extension by striking the edges of the sheet just before end of travel, thus forming them into approximate conformance with the circumference of the tube. The shoulder 15 causes the seam 29 to fold back upon itself downward toward the lower half of the tube, while the shoulder 19 forms seam upward toward the upper half.

It should be noted that in place of the sheet 21, which has been cut to the proper size, a continuous strip of material may be fed between the dies, this strip being of the width necessary to form the tube as shown in Figure 2. The strip is cut to length by conventional cutting mechanism, either after forming or simultaneously with forming, and it is then advanced for the next motion of the dies.

When the center tube 22 has been completely formed, as described, it is assembled with the other components of a conventional filter element, such as those described in the aforementioned Bell patent. As shown in Figure 5, the completed element consists of the pack 41, upper end disc 42, lower end disc 43, outer body 44, and the center tube 22. The center tube is inserted in the center of the pack'41 the outer body placed around the pack, and the upper and lower end discs placed on the pack and cemented in place. The inturned portions and 46 of the discs are placed within the center tube for greater strength and to help in preventing the center tube from being inadvertently'removed.

A modification of the invention is shown in Figures 6 and 7. In this form of the invention, the upper die 51 and lower die 52 are similar to the dies 11 and 12 of the principal modification. The die 51 consists of main block 53 which is surmounted by plates 54 that are similar to the plates 14 of the die 11 except that the outer surface 55 is rounded to form a convex crown across its width. Each plate is separated by a gap 56 which extends to a concave channel 57 in the block 53.

The lower die 52 consists of block 58 on which are mounted plates 59 which are crowned at 60 in the same manner as plates 54. The gaps 61 between the plates extend to concave channels 62 in the block 58. The dies are brought together on sheet 63 just as in the principal form of the invention, with the center tube 64 resulting from this operation. This center tube is similar to tube 22 except that each of the circular strips 65 are crowned because of the shape of the die plates. This results in a tubeof higher strength, which is desirable in certain installations.

A further modification of the invention is illustrated in Figures 8 and 9. The upper die 71 and the lower die 72 shown in Figure 8 are similar to the dies 11 and 12 of the principal form of the invention. The die 71 consists of a main block 73 which is surmounted by plates 74 that are similar to the plates 14 of die 11 except that they are mounted at an angle of approximately 5 to the vertical. Each plate is separated by a gap 75, continuing into the block itself to form the channel 76. The lower die 72 consists of block 77 on which plates 78 are also mounted at the same angle as the plates 74 on block 73. These plates are separated by gaps 79 which continue into the block to form channels 80. The dies are brought together in a direction paralleling the line of the plates so that the same action of passing the plates into the gaps will occur as before. The sheet 81 is formed into the ,centertube 82 as in the other operations, except that in this case the semi-circular strips 83 are at an angle of approximately 5 to the longitudinal axis of the tube. As can be clearly seen in Figure 9, this results in a flatter tube end which is desirable in certain installations because the bottom edge of strip 84 is in the same plane (at right angles to the longitudinal axis); and at the same time, strip 85, which is adjacent to strip 84 but on the opposite half of the tube, is partially in the same plane because of its angle. The same holds true for the upper edge. As a result, more than half of the periphery of the tube at its ends lies in the same plane, as contrasted to just half in the other forms.

It is to be understood that the two modified forms of the invention shown as center tubes 64 and 82, may be assembled into a complete element just as tube 21 is shown to be assembled in Figure 5.

It should be understood that my novel center tube may be used in conjunction with other types of filter media. For example, instead of the convoluted paper pack 41, the medium may be a mass of fibrous material such as cotton waste. Another example might be a series of stacked discs. Both of these media are well known in the filtering art. The advantage of using my invention with such media is the added rigidity coupled with the large open area.

Thus it is seen that by practicing my invention, it is possible to make an inexpensive center tube in a very simple fashion by the use of a one step die operation. The resulting part will be eificient to manufacture because no material is lost in the process, and will be eflicient to use because of the large percentage of open area.

I do not intend to be limited to the specific embodiments of my invention shown herein, but I wish toinclude in my inventive concept any variations in structure such as may be made by anyone skilled in the art.

What is claimed is:

1. In a filter element comprising an annular filter pack, a one-piece cylindrical tube inserted in the center of the pack, said tube consisting of formed semi-circular strips of material constituting approximately one-half of the tube, said strips equally divided between the two demicylinders of said tube, each strip separated by a gap from its adjacent strip, and two diametrically opposite scams extending along the length of the tube which interconnect and follow the curve of said strips.

2. In a filter element comprising an annular filter pack, a one-piece cylindrical tube inserted in the center of said pack, said tube consisting of formed semi-circular strips of material which constitute approximately one-half of the tube, half of said strips lying in one demi-cylinder of said tube and the other half of said strips lying in the other demi-cylinder of said tube, each adjacent pair of strips in each derni-cylinder separated by a gap equal in width to and aligned with a strip in the opposite demicylinder, and two diametrically opposite seams extending along the length of the tube each seam joining one end of each strip, said seams following the curvature of said strips.

3. In a filter element comprising an annular filter pack, a one piece cylindrical tube inserted in the center of said pack, said tube comprising two seams located diametrically opposite each other, running the length of the tube and forming a portion thereof, said seams being interconnected by a plurality of semicircular strips, approximately one half of said strips forming one half of the tube and separated by gaps and the remainder of said strips forming the remainder of said tube and also separated by gaps, said first named strips being radially aligned with the gaps between the second named strips and said seams conforming to the curvature of said strips.

4. In a filter element comprising a filter pack, a one piece cylindrical tube within said pack, said tube consisting of semi-circular strips of material consitituting approximately one half of the tube, said strips being distributed between the two demi-cylinders of the tube,.each

strip being separated by a gap from its adjacent strip, and diametrically opposite seams extending along the length of the tube which interconnect and follow the curvature of said strips.

5. In a filter element comprising a filter pack, a one piece tube within said pack, said tube consisting of oppositely directed bent out strips of material constituting approximately one half of the tube, said strips being divided between two derni-portions of the tube, each strip being separated by a gap from its adjacent strip, and two diametrically opposite seams extending along the length of the tube which interconnect the strips and follow the peripheral bends of said strips.

References Cited in the file of this patent UNITED STATES PATENTS 493,791 Schurig Mar. 21, 1893 979,403 Wensley- Dec. 20, 1910 1,405,042 Kraft Ian. 31, 1922 1,453,082 Rosenberg Apr. 24, 1923 1,878,055 Wittlifi Sept. 20, 1932 2,642,187 Bell .a June 16, 1953 

